(1) Field of the Invention
The present invention relates to an optical print head (PH) that performs writing onto a photoreceptor by an optical beam and an image forming apparatus including the optical PH.
(2) Related Art
Some of image forming apparatuses such as printers include an optical PH that writes an image onto a photoreceptor by an optical beam emitted from each of minute light-emitting elements that are arranged in line.
Japanese Patent Application Publication No. 2005-144686 discloses, as an optical PH, a line head including a large number of organic EL elements as light-emitting elements that are arranged on a substrate in a main scanning direction.
Such a line head has a configuration in which a parallel circuit is arranged on the substrate, which is composed of the organic EL elements each having an anode connected with a power line A on a power source side and a cathode connected with a power line B on a ground side. Also, a moisture-proof plate is provided spaced from the substrate, and has wired thereon an auxiliary power line C on the power source side and an auxiliary power line D on the ground side.
The line head has a circuit configuration in which an increased number of power feeding points for the organic EL elements are provided by electrically connecting the power line A on the substrate with the auxiliary power line C on the moisture-proof plate at a plurality of points and electrically connecting the power line B on the substrate with the auxiliary power line D on the moisture-proof plate at a plurality of points.
With this circuit configuration in which an increased number of power feeding points are provided, it is possible to shorten a wiring distance on the power line from one power feeding point to each of the organic EL elements compared with the configuration in which a less number of power feeding points are provided. Since there is a less potential drop due to a wiring resistance, it is possible to decrease a difference in supply current between the organic EL elements caused by the potential drop, thereby suppressing unevenness in light emission amount between the organic EL elements.
However, even if the configuration is adopted in which a certain increased number of power feeding points are provided as in the configuration disclosed in the above patent application publication, there is no change that a potential drop occurs on a part of a power line between each two adjacent power feeding points in the current flowing direction. Accordingly, a problem still remains that unevenness in light emission amount due to the potential drop is not eliminated.